الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
Abstract
Microbiologically influenced corrosion (MIC) is a type of corrosion which affected by presence and activities of microorganisms, MIC assisted and caused corrosion failures in many industries especially in petroleum fields.
Sulfate Reducing Bacteria (SRB), the main cause of MIC in oilfield systems, are widespread in both seawater and freshwater. In the oil production field, water flooding was carried out as a secondary recovery process. Meanwhile, the water injected provided a proper environment for SRB proliferation.
Thus, there is an urgent need to elucidate MIC mechanism and then develop effective mitigation approaches.
The present study was divided into three parts based on the specific objectives:
(1) Sampling of a formation water from an oil field production tank, suffering from severe metal corrosion problems, in order to collect mixed culture of sulphate reducing bacteria SRB.
Summary 139
(2) Identification of The microbial communities via metagenomic analysis by Next Generation Sequencing (NSG) technique.
(3) Synthesis of a novel Schiff base cationic surfactants, and applying it to eliminate the microbial induced corrosion.
Thus, in the present study, we can conclude that:
Part I: Collection of formation water samples from Egyptian oilfield:
In order to collect mixed culture of sulphate reducing bacteria SRB; a formation water samples were collected from an oil field production tank, located in North Bahrya Petroleum Company (NORPETCO), Western desert, Egypt. This tank was known to be suffering from a severe metal corrosion problems.
The isolation of mixed SRB culture was carried out immediately in the field by inoculating the collected water samples in an anaerobic selective Postgate´s-B medium, the samples were transferred to the laboratory undercooling and anaerobic conditions for further analyses.
Summary 140
The growth count of SRB isolated from the aseptically collected sample was found to be 105 bacterial cells/ml.
Part II: Identification of The metagenome of microbial communities by Next Generation Sequencing (NSG) technique:
from the data of metagenomic analysis we can concluded that the formation water sample has a high degree of microbial variation. It was found that a total of 6 phyla across all sample were identified, Proteobacteria, Firmicutes, Synergistetes, Thermotogae, Bacteroidetes and Spirochaetes. Among all these phyla, Proteobacteria was most dominant with 60% reads followed by Firmicutes (20%), Synergistetes (11%) and Thermotogae (5%). Other important phyla like Bacteroidetes and Spirochaetes comprised of 2% sequencing reads. Although 43 different families have been observed across the sample, the sample was overwhelmingly dominated by Desulfovibrionaceae at the family level, which was found to be about (53%) of total reads.
Summary 141
In the genus level, about 31 genera were detected, and most of the species belonged to Desulfovibrio, representing about 53%. At the species level, Desulfovibrio alaskensis was found to be the most predominant sulphate reducing bacteria in the collected sample. This results in agreement with our expectations, and explained the sever microbial corrosion in petroleum field we chooses to study.
Part III: Application of different novel synthesized surfactants to eliminate the microbial corrosion.
Three Schiff base cationic surfactants coded (Q12, Q14 and Q18) were synthesized and characterized using FT-IR and1H-NMR techniques, and the surface activities of these compounds were studied.
The surface tension of the new synthesized surfactants in aqueous medium had been studied, and the results of surface tension was 29, 31and 34 mN/m for Q18, Q14 and Q12
Summary 142
respectively, comparing with surface tension of distilled water (73 mN/m).
Also the surface activity parameters such as Specific conductivity, Critical micelle concentration, maximum surface excess, effectiveness, and the degree of counter ion dissociation and free energy of micellization of the synthesized surfactants had been studied, which is fundamental character to their various applications.
The antimicrobial activity of synthesized surfactants against isolated Sulfate Reducing Bacteria were carried out by different methods.
The results revealed that synthesized surfactants have a high inhibition effect from 4.6×106 and 3.8×105 cell/ml for control1 and control2 respectively until the number of bacterial cell count were reduced to 1.5×102, 9.3×102 and 1.2×102 cell/ml for Q12, Q14 and Q18 respectively after one month of cultivation with dose of 500 ppm. Also it revealed completely inhibition effect with higher doses.
Summary 143
A considerable decline in the biogenic sulfide concentration from dose of 500 ppm until achieving a complete suppression at doses of 1000 ppm.
The efficiency of synthesized surfactants to mitigate the microbial corrosion has also been confirmed by examining the metal surface under Scanning Electron Microscopy SEM, the SEM-images of the coupons treated by surfactants revealed that the coupons’ surfaces were free of biofilm and iron sulfide by comparison with untreated coupons.
Weight loss, corrosion rate and corrosion inhibition efficiency of the new synthesized cationic surfactants has also been studied. Our finding proved that the prepared cationic surfactants with longer hydrophobic chains expressed an efficient corrosion inhibition as well as functioning as bactericides. Also the inhibition efficiency of these compounds for carbon steel corrosion was comparative to, and even better than, many ordinary cationic or anionic surfactants.
conclusion 144
CONCLUSION
In this study, a formation water sample was collected from an oil field production tank, suffering from severe metal corrosion problems, in order to collect mixed culture of sulphate reducing bacteria SRB.
This study sheds light on bacterial communities that initiate and accelerate microbial corrosion of the carbon steel in petroleum fields.
The microbial communities were identified via metagenomic analysis by next generation sequencing technique. We identified about 6 phyla across all sample, Proteobacteria, Firmicutes, Synergistetes, Thermotogae, Bacteroidetes and Spirochaetes. Among all these phyla, Proteobacteria was most dominant with 60% of total reads. The collected sample was dominated by Desulfovibrionaceae at the family level, which was found to be about (53%) of total reads.
The bacterial communities capable of forming biofilm on the carbon steel metal surface in biotic system.
In this study, three Schiff base cationic surfactants were synthesized and characterized using FT-IR and1H-NMR